This application claims a priority from German application DE 101 27 990.6-52, filed on Jun. 8, 2001, and the contents of that application are incorporated herein by reference.
This invention concerns apparatus for detecting moisture of a type including an LC-oscillating circuit as a transducer, an oscillator for exciting the oscillating circuit, a tuning device for frequency-wise tuning of the oscillator, and a measuring and evaluation circuit to determine the attenuation, or dampened, condition of the oscillator and to provide a signal that is proportional to a relative, or degree of, moisture of the transducer.
Such a device for recognizing, or determining, moisture is disclosed in German Patent document DE 44 26 736 A1.
With the help of such a device, or such a sensor system, a windshield wiper of a motor vehicle can be controlled depending on an amount of rain, for example.
Known devices for determining moisture of the type described in German Patent document DE 44 26 736 A1, as well as known corresponding optical, resistive and capacitive sensor systems for determining moisture in other technical prior art, all have the disadvantage that they must be attached to a windshield of a motor vehicle in an expensive manner. The cost of electronic components for transducers is relatively great, which represents a particular disadvantage for fabrication of, as well as the breaking of, motor-vehicle windshields. Optical sensor systems have the additional disadvantage that they are very sensitive to dirt contamination, and therefore, an output signal of a measuring and evaluation circuit often can no longer be trusted as being a measurement of the degree of moisture at the transducer.
It is an object of this invention to provide a device for determining moisture that allows the greatest degree of freedom for mounting the transducer and with the transducer having the fewest possible electronic components, while it is also possible to assemble the measuring and evaluation circuit substantially independently of the transducer. In addition, it is an object of this invention to provide uses for such a device for determining moisture.